Field of the Invention
The invention relates to an optical apparatus, and more particularly, to a display apparatus.
Description of Related Art
A light source module is usually used together with a display panel incapable of emitting light by itself, such as an electrophoretic display panel and a liquid crystal display panel, so as to allow a display apparatus to be watched in low light environments. For a transmissive liquid crystal display panel, a backlight module is usually disposed at back of the transmissive liquid crystal display panel to provide sufficient illumination for the transmissive liquid crystal display panel. On the other hand, for a transmissive reflective electrophoretic display panel (e.g., an electronic paper) or a reflective liquid crystal display panel, a frontlight module is usually disposed at front of the transmissive reflective electrophoretic display panel, so as to provide sufficient illumination for the transmissive liquid crystal display panel.
With current existing technology, it often requires an additional light source to provide illumination for outside a non-display area. Therefore, the additional light source may occupy a specific volume inside the display apparatus and prone to crowding-out of space for a light guide plate of a display area. On the other hand, in case illumination for the non-display area is used to light up a transmissive icon area, a upside emitting light source located below the transmissive icon area may be used to provide illumination for the non-display area. Therefore, a relatively larger space near the transmissive icon area is generally reserved for accommodating said light source. In this case, if the light guide plate providing illumination for the display area is also at the same direction, it is prone to crowding-out effect in which a light mixing area originally used by the light guide plate may be shorten, resulting in that the display area is prone to a hot spot phenomenon in terms of optical design. In other words, a non-uniform brightness may occur at positions closing to the light source.
More specifically, in a side incident type frontlight module, a light emitting element (such as a cold cathode fluorescent tube (CCFL)) may be disposed on an incident surface located on a lateral side of the light guide plate. After passing through the incident surface and entering the light guide plate, a light beam from the cold cathode fluorescent tube may be scattered by microstructures on the light guide plate into a planar light source having a uniform brightness to provide illumination for the display panel. With breakthrough in processing technology, a light emitting diode (LED) is gradually replacing the cold cathode fluorescent tube to serve as the light emitting element used in the frontlight module. In conventional design, a plurality of light emitting diodes are arranged near the incident surface of the light guide plate and spaced apart from one another. However, since the light emitting diodes are of a spot light source, a light intensity provided near the incident surface may not be uniformly distributed. Therein, a light region may be formed at positions facing right at the light emitting diodes, and a dark region may be formed between adjacent two of the light emitting diodes. As a result, a non-uniform distribution of the light intensity may occur on the light guide plate near the incident surface and known as the hot spot phenomenon. The hot spot phenomenon may be even more serious in case a light mixing distance is not long enough.